Some of devices for controlling a motor of a usual motor controller have a function for identifying an inertia (for instance, see Patent Document 1).
A device proposed by the applicant of the present application is provided with a speed control unit for determining a torque command and controlling a speed of a motor so that an inputted speed command corresponds to the actual speed of the motor, an estimating unit for simulating the speed control unit so that the speed of a model corresponds to the speed of the motor and an identifying unit for identifying an inertia from a ratio of a value obtained by time integrating in a prescribed section the absolute value of a value obtained by passing a speed tracking error of the speed control unit through a prescribed filter to a value obtained by time integrating the absolute value of a speed tracking error of the estimating unit in the same section, and only when the speed tracking error of the estimating unit is zero or speed in the estimating unit is not zero, a calculation for identifying the inertia is carried out in the identifying unit.
In this device, since an identifying operation can be performed in real time for an arbitrary speed command, even when the inertia changes with respect to time, the inertia can be identified.
Patent Document 1: JP-B2-3185857 (page 3, FIG. 1)